Ocean acidification afected marine organisms especially calcifying organisms, such as Halimeda sp. This study was conducted on June to September 2012 at laboratory of Research Center and Development for Marine, Coastal and Small Islands, Hasanuddin University. The aim of study to determine the efect of acidic level on Calcium concentration and growth rate of calcifying macroalgae, Halimeda sp. The experiment design was used completely random design with three treatments and three replicates. Analysis variance was used for data analysis with advanced respon test. Tukey test was used to compare the diference between treatments. Water quality parameters were analyzed descriptively. The results showed that there was a significant diference of pH treatments on calcium concentration an d growth rate of Halimeda sp. The highest calcium concentration was found at pH 8. In conclusion, increasing pH level of media disturbed the calcifying process of Halimeda sp especially at pH level of 6, while growth rate of Halimeda sp was not afected wit h the decreasing of pH.

There has been limited systematic monitoring of seaweed growth with simultaneous measurement of important yield determinants. This study reports on Kappaphycus alvarezii (Cottonii) seaweed experiments in South Sulawesi, Indonesia. The first (June – Oct 2023) experiment showed lower yields for the lowest seedling weight and similar yields for the medium/high seedling weight. During this period, seaweed losses from lines (empty ties), ice-ice disease and fouling by epiphytes increased. The second experiment (March – July 2024) showed high yields for the traditional longline and low yields with tube-nets and cages, due to fouling by epiphytes and mud. Yields did not differ systematically between villages and did not differ systematically between nearshore and further offshore. Yields were highest for planting in March and lowest for planting in August. Stronger winds and rougher sea towards October were shown to be an important yield determinant, but not the only one. During the March-October period losses from lines increased, pressure from the ice-ice disease increased, fouling by mud and epiphytes increased, temperatures decreased and windspeed increased. Yields in the March-October cultivation cycles were determined by a combination of the effects of these five yield determinants. To our best knowledge the current study is the first to study this full range of possible yield determinants and to simultaneously monitor for longer period (five cycles, with bi-weekly sampling) both seaweed biomass and yield determinants.

Microplastics is a problem that has been concerning, especially in marine habitat. The presence of microplastics in large quantities will have an impact on the environment and marine organisms. Marine organisms that are vulnerable to contamination by microplastics pollutants namely green mussels (Perna viridis). This study aims to determine the microplastics forms and concentration found in green mussels (Perna viridis) in Maccini Baji Waters, Labakkang District, Pangkejene Kepulauan Regency, South Sulawesi. The sampling of the mussels was carried out by the method of purposive random sampling with the sample was grouped into 3 groups of shells lengths, namely 2-3.9 cm, 4-5.9 cm and 6-7.9 cm with 33 individuals for each group. Microplastics observations were carried out using a stereo microscope. In addition to analyze microplastics concentrations, an analysis of the frequency of microplastics presence in shells was also carried out. The results showed that the microplastics was found in the form of fiber and fragments with several colors namely clear white, blue, black, red, and purple. The frequency of microplastics presence in green mussels was above 50% with an average of 71.7% exposure to microplastics. The highest frequency of microplastics presence and concentration in the range of shell lengths accounting for 2-3.9 cm.

The Bio Economic Seaweed Model (BESeM) is a model designed for modelling tropical seaweed cultivation. BESeM can simulate the common tropical seaweed cultivation system with multiple harvests per year, clonal reproduction and labour intensive harvesting and replanting activities. Biomass growth is modelled as a sigmoid, with growth being initially exponentially and eventually flattening off towards a maximum weight per plant or per square meter (w_f,max). To estimate the latter, longer duration experiments than normal are needed – in the order of 100 days rather than 45 days. Drying (on platforms on the beach) is simulated as well as increase in harvested chemical concentration over time since planting, for harvested chemicals such as agar extracted from Gracilaria or carrageenan extracted from Kappaphycus or Euchema. BESeM has a limited number of parameters which makes it easily amenable to new sites and species. An experiment is presented for a site in Indonesia in which Gracilaria was monitored for 120 days in 6 nearby sites and from which BESeM model parameters were estimated. A simulation example is presented which illustrates how BESeM can be used to find the optimum combination of replanting weight and harvest cycle length (in days) for maximising gross and net farm income.